Assembling fan blades and rims



Nov. 17, 1942.

M. J. BARTCH ASSEMBLING FAN BLADES AND RIMS Filed Nov. 1, 1940 2 Sheets-Sheet l INVENTO/f mm 1 BARTCH BW- ,4

ATTORNE ys Nov. 17, 1942; M J BARTCH 2,302,095

ASSEMBLING FAN BLADES AND RIMS 7 Filed Nov. 1, 1940 2 Sheets-Sheet? .ILTEZIU IMF/770R mum I BARTCH 1W Q ML 4 TTOR/VEYS Patented Nov. 17, 1942 ASSEMBLING FAN BLADES AND RIMS Maura J. Bartch, Detroit, Mich., assignor to American Blower Corporation, Detroit, Micln, a corporation of Delaware Application November 1, 1940, Serial No. 363,929 fi 4 Claims. (Cl. 29-1563) The present invention relates to a' method of making air-handling apparatus and more particularly the fan or impeller employed therein.

In the case of centrifugal blowers squirrel cage fans are sometimes used in which the fan wheel is constituted of a pair of spaced end rims or rings with blades, usually of an arcuate configuration interposed between the spaced rims and secured theretoin any suitable manner. In still other types of fans, the blades are secured to aback plate. The ends of the blades are often welded or riveted to the inner surfaces of the rims or back plate in order to form a rigid composite body. However, a fan made in accordance with this technique is expensive, not only due to the slowness with which the same must be assembled and fabricated, but also on account of calling for highly skilled labor in making the weld or performing the riveting operation. The cost of the finished fan increases in direct proportion to the number of blades and therefore in the number of joints which must be made so that inthe case of those fans having a large number of blades, twenty-five or more, the cost of the same is almost prohibitive. While the greatest, advantages of the invention described hereinafter are present in. connection with fans having a large number of blades it will be understood that the invention offers certain advantages even in the case of fans having a relatively small number of blades.

The primary object of my invention is to provide a method of manufacture whereby a. fan of the centrifugal type can be made at a less cost than those on the market, necessitating only ordinary skill in assembly and manufacture. Another object is to provide a method of making afan in which the-blades are secured to the end plates or rims without the necessity for welding, and yet the joint is equally as good as that obtained by a weld. I

These objects are attained in brief, by providing a purely mechanical joint between the ends of the blades and the rims. The blades are provided with one or more projections at the ends and extruded openings are formed in the rims in line with the projections. These extrusions are of such character as to constitute a guideway for each blade projection so that after the projection has been inserted in place, the

extruded metal may be flattened out to form a rivet. Other objects and features will be apparent as the specification is perused in connection with i the accompanying drawings, in which Figure 1 represents a cross-section through a fan wheel constructed in accordance with the invention and positioned within a centrifugal blower.

Figures 2 and 3 are plan and edge views respectively, of the improved rim ready to receive the fan blades,

Figures 4 and 5 are views showing a blank from which the finished rim is made.

Figures 6 and 7 are end and plan views respectively, of a blade which may be advantageously employed in connection with the openings of the rim shown in Figures 2 and 3.

Figure 8 isan enlarged and fragmentary plan view of the extruded or pierced openings formed in the improved rims.

Figure 9 is a sectional view taken along line 99 in Figure 8 to show the guiding effects of the extruded or upset metal surrounding the openings in the rim.

Figure 10 shows in elevation, a jig or frame for holding the fan wheel in place during one of the manufacturing operations. a

Figure 11 is a fragmentary sectional view out through a pair of rims to show the effect of peening the blade projections over the extruded openings in the rim. Each half of Figure 11 represents a sectional view taken along line ll ll in Figure 12.

Figure 12 is an enlarged plan but fragmentary view looking at the outside of the improved rim and showing the eifectsof peening a limited number of the blade projections positioned in the openings of the fan rim.

Figure 13 is a sectional view illustrating the riveting effects between the fan blades and the rim, while Figure 14 is a plan view looking down on the riveted elements.

Referring to the drawings in detail, numeral I represents a sheet metal casing of volute configuration and provided at its ends with a pair of openings into which is fitted the arcuate cylindrical members 2, which form the only inlet to the casing I. The latter is provided with an outlet- (not shown) at that part of the volute which is of greatest diameter as is customary in the art. openings provided in the hollow cylinders 2, there is a shaft 3, which is driven preferably by an electric motor (not shown).

Theimproved fan wheel which is generally designated .by the reference character 4 i mounted on a shaft for rotation within the casing I. This fan wheel is of the so-called squirrel cage type in which air is drawn in from both ends and is expelled from the periphery of the fan.

The fan blades 5 have a length almost as wide Concentrically mounted within the will be described presently. These rims as seen I in Figure 2 are constituted of a ring element which is spanned at thre places by spokes I converging at the center in a hubB. A relatively heavy metal ring 9 (Figure 1) is secured to the hub portion 8 in any suitable manner, for example by the screws Hi, this hub portion being keyed and rigidly secured to the shaft 3.

The rim and spokes are blanked out or sheet iron and therefore are planar in form, as seen in Figures 4 and 5. Three arcuate slots II at the periphery of the blank, also three screw openings (2 at the hub of the blank are formed simultaneously during the blanking operation. The purpose of the slots will be explained.

The next step in the process is to twist the spokes I out of alignment from the rim 6, the amount of twist being preferably of about 23 and the direction of the twist depending on the direction of rotation of the fan wheel. The twist of the spokes serves two purposes.

(1) It provides an eifective fan action at the inlet openings tending to increase the force with which air is drawn through the inlets, and

(2) Serves to increase the rigidity of the spokes so that the latter may be initially formed as a relatively narrow element (thus impeding the incoming air as little as possible) and yet when twisted out of alignment with the rim, the spokes are given added rigidity by which to support the fan wheel on the shaft. The twisted portions of the spokes are indicated at 13 in Figure 3.

A fan wheel of the type shown may comprise as many as fifty or more or as few as fifteen blades all of which must be quickly assembled in proper position, and rigidly secured to the rims in as simple a manner as possible and without necessitating highly skilled labor.

In accordance with one of the features of the present invention, an improved mechanical joint is provided between the ends of the blades and each rim. As seen in Figure 7, the arcuate blades 5 are provided at each end with a pair of tabs or projections H, the length of which is considerably greater than the thickness of the rim 6. The latter has formed therein, preferably at the time of the original blanking operation, a number of extruded openings l5 and in which the extruded metal is forced outwardly from the rim away from the fan blades. These openings may be provided in any suittable manner but I prefer to pierce the metal by a suitably formed punch, so that none or at least very little of the metal will be removed from the rim but the metal will take the form of an upset portion indicated at is, surrounding the opening left by the punch. The latter should have a configuration in size suilicient to provide an opening which will readily receive theprojections ll of the fan blades upon initial insertion and tightly receive the projections upon complete insertion.

As shown in Figure 8, these openings are of an arcuate configuration to correspond with the curvature of the blades and as many openings are provided, per blade, as the number 01'. projections on the end of the blade. It is apparent that the piercing operation may be performed the latter may be supported on a pair; of spaced frame heads I! (Figure bolted to a base l9. In order to align the two rims with respect to one another so as to bring the openings l5 into register and therefore adapted to receive the ends of the blades 3, aligning lugs (not shown) may be provided on the fixture which lugs lit in the slots H. The rims are thus held in proper position so that the blades in the completed wheel will be parallel to the axis of rotation. The openings IS in one of the rims 6 are made to fit snugly upon the projections I! to position the blades upon equal radii from the center of the rims 6 and to set the blades at aproper working angle.

The next step is to assemble the blades, and as pointed out hereinbefore, the projections I4 may be readily inserted into the openings l5, due to the guiding effects of the enlarged rounded edges formed about these openings during the piercing or extruding operation. The facility with which the blades can be caused to enter the openings I5, is illustrated in Figure 9. It should be noted in this respect that even if the projections ll are left with burrs or other overhanging edges during the forming operations, the ends of the blades can still be readily inserted into the openings l5 of the rims, due to the taper provided at the inner edges of the openings. Inasmuch as the depth of the projections I4 is greater than the thickness of the rims, a portion of the projections M will extend, at least slightly, beyond the outer surface of the extruded or upset metal.

After several of the fan blades have been assembled and inserted in the rims, the next step is temporarily to secure the rims to the blades and to one another. This is done preferablyby a peening operation, i. e., by causing a wedge shaped tool or chisel to enter the ends of the projected blade portions which produces a wedging effect at these projections. A suitable form of fixture for facilitating the peening operation is shown in Figure 10 in which the left-hand,

At the right-hand end of the fan wheel there may be provided, a peening tool 23 similar in shape to the member 12,.and adapted to be held in the hand and struck by a hammer. It is apparent that a workman by holding the tool 23v and striking the tool a hammer blow will simul-';

taneously peen a pair of projections at both ends of the wheel. while all of the projections may be peened, if desired, I prefer'to perform this operation only on a limited number of projections. As seen in Figure 12, one out of every four to eight of the outer projections and the same num- .ber of inner projections, are peened. It will be understood that the outer and inner projections are peened simultaneously by the pair of peening simultaneously with the punching operation by tools 21 and 23. The effect of the poem P tion is to wedge the projections I 4 within the openings I5 as seen in Figure 11, so that the rims 6 are securely but temporarily held together on the shaft I! and the blades are all in place.

The next step of the operation is to rivet the ends of the projections, including those which had been previously split. This can be conveniently accomplished by the use of riveting hammers which causes the metal which projects beyond the outer surface of the rims, to be flattened and pinched against the rim, thus permanently binding the wheel parts together into a rigid unit.

The flattening effect of the riveting operation is shown in Figures 13 and 14.

It will be noted that my improved technique of fabricating a fan wheel, requires only the elementary mechanical operations, in that the extruded openings It may be rapidly formed in the same punching operation that provides the original rim blanks.

The assembly operation may be quickly performed since it is no longer necessary to fish" for the openings in the rims in order to insert the blade projections therein, but instead, the extruded metal forms a guideway for the projections and incidentally, removes any slight obstruction such as the effect of bur-rs, which might be present at the edges of the projections. I

The peening or wedgingoperation shown in Figures 10, 11 and 12 also the riveting or flattening operation shown in Figures 13 and 14 require nothing more than ordinary mechanical skill, so that fan wheels of the improved character can be fabricated at much less expense than those of the prior art, which require for assembly a welded joint between the ends of each blade and the rim.' It should also be noted that by forming the openings l5 as an extrusion or piercing eifect, practically none of the metal of the rim, is lost, but the extruded metal together with that portion of the blade projection which extends beyond the rim, is employed for the riveting operation.

A smoother or more refined job results in the preparation of openings l5 by a combination of punching and extruding, the punch taking out not more than the amount of metal in a cross area of the bladeprojection, thus permitting the portions of the rim IE to be pushed back in the plane of the rim, during the riveting process, resulting in a fini'shed 'job as shown in Figure 13.

While I have described my invention more particularly in connection with a fan wheel of the squirrel cage type in which the fan blades are positioned between a pair of rims, it will be understood that the invention is not limited to a fan construction of this type. Indeed the improved structure can be used in connection with all sorts of fans in which it is desired to secure the end or other projecting elements on a fanrims, the method which consists of forming.

tenons on the ends of the fan blades and a shoulder to establish the length of the tenon, of piercing the rims to form flanged openings'therein having a throat substantially larger in crosspermit movement of the assembly during proc- ;ess' of manufacture, and'then permanently securing th ends of the tenons to the rims by compressing the tenons longitudinally to form a head that engages-the upturned edge metal of the flanged openings to force the edge metal into the plane of the rims in engagement with the tenon shoulders and transversely squeeze the tenons.

2. In' the art of manufacturing fan wheels having blades secured between a pair of circular rims, the method which consists of forming tenons on the ends of the fan blades and a shoulder to establish the length of the tenon, of piercing the rims to form flanged openings therein having a throat substantially larger in crosssectional area than the cross-sectional area of the tenons on the blades and which gradually decreases in size to the same cross-sectional area as the area of the tenons, inserting the tenons into the pierced openings through the throat thereof until the tenons extend through the smallest cross-sectional area of the openings to radially position the blades upon the rims and the tenonshoulders engage the rims, splitting some of the tenons longitudinally to wedge the tenons so split within the openings to provide a fan assembly which is temporarily secured together to permit movement of the assembly dur-' ing process of manufacture, and then permanently securing the tenons to the rims by compressing thez'tenons to produce a head on the same on the outer side of the rims and simultaneously returning the flanged edge metal around the openings into the plane of the rim to engage the tenon shoulders to transversely squeeze the tenons and secure the rims between the heads and the tenon shoulders.

3. In the art of manufacturing fan wheels having blades secured between a pair of circular rims, the method which consists of forming tenons on the ends of the fan blades and a shoulder to establish the length of the tenon, of piercing the rims to form flanged openings therein having a throat substantially larger in crosssectional area than the cross-sectional area of the tenons on the blades and which gradually decreases in site to the same cross-sectional area as the. area oi the tenons, inserting the tenons into the pierced openings through the throat thereof until the tenons extend through the smallest cross-sectional area of the openings to radially position the blades upon the rims and the tenon shoulders engage the rims, splitting some of the tenons longitudinally to wedge the tenons so split within the openings to provide a fan assembly which is temporarily secured together to permit movement of the assembly during process of manufacture, and then securing the tenons to the rims by compresing the tenons to head the same and simultaneously return the flanged edge metal around the openings into the plane or the rim by the heading operation to engage the tencn shoulders and to transversely squeeze the tenons. g

4. In the art of manufacturing fan wheels having blades secured between a pair of planar circular rims, the method which consists of forming tenons on the ends of the fan blades and a shoulder to establish the length 01 the tenon, of piercing the rims to form flanged openings therein equally spaced radially from the axis of the rims and having a throat substantially larger in cross-sectional area than the cross-sectional area of the tenons on the blades and which gradually decreases in size to the same crossthe throat thereof until the tenons extend through the smallest cross-sectional area or the openings to radially position the blades upon the rims and the tenon shoulders engage the rims, splitting some of the tenons longitudinally to wedge the tenons so split within the openings to provide a fan assembly which is temporarily secured together to permit movement of the assembly during process of manufacture, and then permanently securing the ends or the tenons to the rims by compressing the tenons to head the same and compress the edge metal of the openings to force the same into engagement with the tenon shoulders and transversely squeeze the sectional area as the area of the tenons, insert- 15 tenons.

ing the tenons into the pierced openings through 2' MAURA J. BARTCH. 

